1. Field of the Invention
This invention relates generally to the loading of cargo, and is more particularly concerned with a method and apparatus for efficiently loading chip- or plate-like materials into a cargo space.
2. Discussion of the Prior Art
In loading ships, railroad cars, or other shipping means, it is desirable to make maximum use of the cubic space available for greater efficiency in shipping. When dense, or heavy, products are being loaded, it is easy to achieve the maximum weight limit without particular concern for the manner of loading. When light-weight products are to be loaded, however, the product must be packed tightly in order to approach the weight limit.
Some products are relatively easy to pack together. Rectangular boxes, for example, will be stacked tightly, and virtually no space will be wasted. Other products are more difficult to pack tightly. Products such as wood chips are too small to be packed one-by-one, but must be delivered to a space by some form of high speed delivery means. With such a delivery means, wood chips, or other chip- or plate-like materials, will not stack neatly, but will be randomly disposed, leaving large air gaps.
To illustrate the looseness of the packing of chip- or plate-like materials, wood chips weigh about 26 pounds per cubic foot, or 417 kilograms per cubic meter. Ocean going vessels and barges are most often designed to allow 50 cubic feet, or 4.6 cubic meters, per metric ton. Thus, wood chips ought to stow at about 85 cubic feet, or 7.9 cubic meters, per metric ton. Due to the loose packing of wood chips, however, they tend to stow at about 97 to 104 cubic feet, or 9 to 9.7 cubic meters, per metric ton. The extra volume is due to air space caused by the random distribution of the wood chips.
Many efforts have been made to stow wood chips at a lower volume per ton. The chips have been simply dropped into the cargo vessel, then moved around using bulldozers and the like, but this technique does little or nothing to compact the chips. Another technique is to utilize an air conveyor and to blow the chips into all parts of the cargo space. While this may literally fill all portions of the cargo vessel, it does not compact the chips, so the weight per unit volume is not improved. Further, high speed spinners have been used to throw the chips into all areas of the cargo space. Again, this technique may fill the cargo space, but it has not been found to increase the weight per unit volume. Additionally, vibrators have been used in an effort to compact the chips after loading, and these have failed to achieve any great improvement.